test.py: First step towards support of caching dart2js compilations across runtimes

tests/utils/dependency_graph_test.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:expect/expect.dart';
+
+import '../../tools/testing/dart/dependency_graph.dart' as graph;
+
+main() {
+  var dgraph = new graph.Graph();
+  var numberOfEvents = 0;
+  var eventAssertions = [];
+
+  graph.Node newNode(int i, List deps) {
+    graph.Node node = dgraph.newNode(i, deps);
+    Expect.isTrue(node.userData == i);
+    Expect.isTrue(dgraph.nodes.contains(node));
+    for (var dep in deps) {
+      Expect.isTrue(node.dependencies.contains(dep));
+      Expect.isTrue(dep.neededFor.contains(node));
+    }
+
+    numberOfEvents++;
+    eventAssertions.add((event) {
+      Expect.isTrue(event is graph.NodeAddedEvent);
+      Expect.isTrue(event.node == node);
+    });
+
+    return node;
+  }
+
+  changeState(graph.Node node, graph.NodeState newState) {
+    var oldState = node.state;
+
+    dgraph.changeState(node, newState);
+    Expect.isTrue(node.state == newState);
+
+    numberOfEvents++;
+    eventAssertions.add((event) {
+      Expect.isTrue(event is graph.StateChangedEvent);
+      Expect.isTrue(event.node == node);
+      Expect.isTrue(event.from == oldState);
+      Expect.isTrue(event.to == newState);
+    });
+  }
+
+  var node1, node2, node3;
+
+  node1 = newNode(1, []);
+  changeState(node1, graph.NodeState.Processing);
+  node2 = newNode(2, [node1]);
+  changeState(node1, graph.NodeState.Successfull);
+  node3 = newNode(3, [node1, node2]);
+  changeState(node2, graph.NodeState.Failed);
+  changeState(node3, graph.NodeState.UnableToRun);
+
+  dgraph.events.take(numberOfEvents).toList()
+      .then((List<graph.GraphEvent> events) {
+    for (var i=0; i<events.length; i++) {
+      eventAssertions[i](events[i]);
+    }
+  });
+}